The study recruited 76 recreational runners participating in events in the city over a period of months in 2017. The researchers stretched out the recruitment cycle to try to correct for any seasonal fluctuations.

The researchers recruited equal numbers of male and female recreational runners who were similar in body mass with a BMI range of 18 to 25 and who an average training schedule of two to five runs per week. There were 24 subjects in the vegan group and 26 in each of the other two groups. They were also young, with an average age of 27 years, plus or minus about four years. None of the runners were habitual smokers.

Before arriving at the testing facility, the runners were asked to not exercise for 24 hours and to maintain their standard diet. After a weigh in and a physical examination, the runners’ diets were assessed via a 24-hour dietary recall conducted with qualified personnel.

Similar energy intake, macronutrient differences

Energy intake for the three groups was similar, at about 9 Mj (9 macro joules, or about 2,150 kcal) per day. The omnivorous group consumed the most protein (about 17% of total calories) and the vegan group the least (about 14%).

But the vegan group consumed significantly more dietary fiber (about 52 grams a day) than did the other two groups, and they consumed significantly less fat (about 15% of total calories, versus between 32% and 33% for the other two groups).

After the physical exam and diet assessment, the participants moved on to the performance measurement portion of the study. In this the subjects exercised to exhaustion on a cycling ergometer. They started with a five minute warm-up at 50 watts power output (equivalent to a slow cruise around the park) and then the power was increased at 16.7 watts each minute. The primary outcomes were the maximum power output ranged against total body weight and against lean body mass.

No difference in exercise capacity

The researchers found no statistically significant difference in the exercise capacity of the three groups. This was the hypothesis they were testing. Additionally, the researchers found no difference between the diet groups when comparing women to women and men to men, though, as stands to reason, the men did generate higher power numbers than did the women.

The researchers said previous studies have compared vegan and omnivorous diets in terms of exercise performance. But this seems to be the first time all three diet styles were compared in a single study.

“To the best of our knowledge, this was the first investigation providing a differential analysis of exercise capacity and lactate/glucose concentrations of vegan, lacto-ovo-vegetarian and omnivorous recreational runners. Our findings that VEG, OMN and LOV show no significant differences in maximum exercise capacity as measured by P​maxBW​ indicate that the evaluated diets do not have detrimental effects on exercise performance in recreational runners,”​ the researchers wrote.

The researchers listed as a limitation the fact that oxygen intake was not measured. Additionally, the use of a cycling ergometer for runners, instead of using a treadmill, could also be considered a limitation, they said.